FIELD OF THE INVENTION
This invention relates to water-containing detergents based on alkali metal hydroxide with a delayed, controlled and variable hardening time. To adjust the solid consistency required, the detergents contain glycols, glycol derivatives and/or certain alkanolamines and alkali metal hydroxide in solid form. The hardening of the water-containing detergent can be delayed by adding paraffin oil and/or surfactants and other components from the group of polyhydroxy compounds in a specific sequence.
Highly alkaline detergents are now commercially available in various forms, for example as powders, granules, liquids, fused blocks or tablets.
Each of these various forms has specific advantages and disadvantages for a given application. Powders, granules and liquids have been successfully used for cleaning textile surfaces or for the manual mechanical cleaning of hard surfaces while tablets or block-form detergents (fused blocks) obtained by melting and subsequent cooling are being increasingly used in addition to powders, granules or liquids for the machine cleaning of hard surfaces, for example for machine dishwashing. Tablets and fused blocks have the advantage over powders of simple, precise "dosing", no dust emission and easy handling.
These advantages may be utilized, for example, in domestic dish-washers, but above all in continuous institutional dishwashing machines in which the articles to be cleaned pass through various washing zones.
It has now been found that very hard tablets and very hard fused blocks have disadvantages. For example, very hard tablets can be damaged by breaking. Tablets damaged in this way naturally no longer have the advantage of precise dosing. Another problem with tablets is that the required solubility in water cannot always be guaranteed, i.e. tablets occasionally dissolve either too quickly or too slowly. Although fused blocks show high fracture resistance in transit, these very hard detergents are problematical to dose from relatively large containers. In addition, both tablets and fused blocks have hitherto required elaborate production processes which, in view of the alkaline melts involved, impose particularly stringent demands on the materials used and the conditions selected.
The detergents obtained are also expected to show a high degree of homogeneity. With solid detergents, however, this is often difficult to achieve. This problem does not affect liquid detergents, which can easily be stirred, as much as it does solid detergents. Accordingly, it would be desirable to have the homogeneity of a liquid, a viscous liquid or a stirrable paste which subsequently hardens into a solid of controllable, variable hardeness in order at this stage to utilize its advantages in regard to storage, transport and dosing. It would be particularly desirable if stirrability could be maintained at temperatures of up to about 40.degree. C. because even temperature-sensitive components could then be added. From the applicational point of view, it would be of particular advantage to prevent premature hardening of the material in the equipment used during the production process. Effective control of the parameters which critically influence the hardening process would be particularly desirable.
The problem addressed by the present invention was to provide highly alkaline general-purpose detergents based on alkali metal hydroxide, preferably sodium or potassium hydroxide, more preferably sodium hydroxide, for textile surfaces, but preferably for cleaning hard surfaces, for example for dishwashing, and in particular detergents for institutional dishwashing machines which would combine the advantages of powders and liquids on the one hand and the advantages of tablets and fused blocks on the other hand. In other words, the problem addressed by the present invention was to provide detergents which would show defined solubility under various in-use conditions, but which on the other hand would be stable in transit and in storage and, in addition, could be dosed quickly, simply and with precision, would not emit any dust and could be produced in a technically simple manner and which would be easy to package. In particular, stirrability during production, hardness variable under control and delayed hardening during production and storage would afford major advantages and would be taken into account. At the same time, the invention set out to provide a process which would enable temperature-sensitive substances to be incorporated, if necessary even below 42.degree. C., without in any way impacting on the other problems addressed by the invention.
The requirements which detergents are expected to meet, such as good cleaning performance, fat dissolving power, etc., would of course also have to be satisfied at the same time.
Both viscous or paste-like detergents and solid detergents in tablet or block form are already known from the prior art.